Problem: $\overline{AC}$ is $3$ units long $\overline{BC}$ is $9$ units long $\overline{AB}$ is $3\sqrt{10}$ units long What is $\cos(\angle ABC)$ ? $A$ $C$ $B$ $3$ $9$ $3\sqrt{10}$
Solution: SOH CAH TOA os = djacent over ypotenuse adjacent $= \overline{BC} = 9$ hypotenuse $= \overline{AB} = 3\sqrt{10}$ $\cos(\angle ABC )=\frac{9}{3\sqrt{10}}$ $=\dfrac{3\sqrt{10} }{10}$